MXPA03002981A - Gypsum decontamination process. - Google Patents

Abstract

A process for reducing a level of radionuclei in a phosphogypsum material having a radioactive contaminant is provided, wherein the process includes the steps of: (a) mixing the phosphogypsum material with an acid decontamination solution to form a mixture; (b) separating the mixture into a liquid stream having a large portion of the radioactive contamination and a solid stream having a residual component of the acid decontamination solution; and (c) removing the residual component of the acid decontamination solution from the solid stream, thus providing a gypsum material that meets or exceeds federal standards for level of radioactive nuclei and providing a process that is environmentally friendly and capable of avoiding the generation of phosphogypsum stacks, as well as eliminating existing or abandoned phosphogypsum stacks, further providing for recovery of the radioactive nuclei if desired.

Description

PROCESS OF DECONTAMINATION OF PLASTER Field of the Invention The present invention relates to processes for removing radioactive nuclei, or radioactive material that occurs naturally (NORM) and more particularly, to a process which eliminates radio, such as radio-226, from of the phosphogypsum material generated during the production of phosphoric acid and which recovers and decontaminates the gypsum. BACKGROUND OF THE INVENTION

[0002] At present, the phosphoric acid yield industry in which the gypsum ore is processed is processed by a wet acid process to produce phosphoric acid, the phosphogypsum paste, often referred to as "gypsum" paste. , is molded by large separation / settlement areas where phosphogypsum solids are separated from liquids. The liquids are then either reused or neutralized and discharged in accordance with state and federal regulations governing the discharge of the plants. The solids remain at the site, and are stored in columns similar to large mounts (which do not find within the context of the present invention, the combination of the separation / settlement area and the mound-like hills we refer to as "piles"), mainly, because the radio-226 level exceeds the regulatory limits of 1 0 picocuries per gram (1 0 pCi / g) established in accordance with the National Emission Standard for Hazardous Air Pollutants or N ESHAP, Title 40, Sections 60,204 to 60,206. , of the Code of Federal Regulations. Alternatively, in the facilities that are located in or very close to the mines of my phosphate neral, the solids can be mixed with an overload and returned to the mines to recover the mines. These solids must be monitored while on the site, and any future use of these solids is severely limited by their radio content. In view of the foregoing, there is a continuing need for environmentally friendly and cost-effective processes, which separate and recover radio-226 from the phosphogypsum solids that produce unregulated phosphogypsum. In addition, there is a continuing need for a process in decontamination or other operations in which nitric acid is used to decontaminate, treat, or otherwise process the material containing phosphogypsum, which includes a step to neutralize or remove other way the residual nitric acid and / or nitrates in the phosphogypsum unregulated, to be used in construction materials or other applications. SUMMARY OF THE INVENTION As a matter of course, an object of the present invention is to provide a process for reducing radionuclide levels in a phosphogypsum material having a radioactive contaminant, the phosphogypsum material being produced in the production of phosphogypsum. phosphoric acid, from the acidic wet processing of the mineral-containing phosphate. It is a further object of the present invention to provide a process for reducing the level of radionuclides in a phosphogypsum material by means of which, the mixing step includes violently stirring the mixture for a specified time duration near the cut level, wherein no destruction of the solids in the phosphogypsum material takes place. Another object of the present invention is to provide a process for reducing the level of radionuclides in a phosphogypsum material wherein the mixing step comprises violently stirring the mixture at room temperature in a range of 21.1 ° C to 37.78 (70 ° C). F to 1 00 ° F) for a certain period of time. A further object of the present invention is to provide a process for reducing the radionuclides of a phosphogypsum material containing a step that eliminates and neutralizes the residual acid in the phosphogypsum of the resulting product. Still another object of the present invention is to provide a process for reducing the level of radionuclides in the phosphogypsum material wherein the process further contemplates the passage of, wash the phosphogypsum material with water, preferably active tank water to form a washed mixture, before mixing the phosphogypsum and the decontamination solution. Subsequently, the process includes the separation of the washed mixture in a liquid stream, and a washed solid stream wherein the solid stream comprises the phosphogypsum material. In addition, the process includes the communication of the washed solid stream to a mixing step where the phosphogypsum and the decontamination solution are mixed. Still another object of the present invention is to provide a process for reducing the level of radionuclides in a phosphogypsum material, as described above, wherein the process further contemplates the passage of, contacting the liquid stream (acid stream that originates from the decontamination solution after mixing it with phosphogypsum and separation), which has a large portion of the radioactive contaminant with an ion exchange resin, or a suitable filter impregnated with a specific ionic resin, to bind the radioactive contaminant to it to effect the removal of the radioactive contaminant to create a regenerated decontamination solution. Subsequently, the process includes returning the regenerated decontamination solution to the mixing step where the phosphogypsum material is mixed with the decontamination solution. Another object of the present invention is to provide a process for reducing the level of radionuclides of the phosphogypsum solids in a phosphogypsum material of a wet acid processing of a mineral-containing phosphate so that: (1) the unregulated phosphogypsum is created whereby a large portion of the radioactive contaminant is removed from the process; (2) The liquid constituents of the process are recovered and recycled in the process.; (3) a portion of decontaminant is recovered and reused; and (4) the decontamination solution is regenerated and recycled. Another object of the present invention is to provide a process for reducing the level of radionuclides of phosphogypsum solids in a phosphogypsum material from a wet acid process of a mineral-containing phosphate, wherein the acid decontamination solution is a solution of nitric acid, and the radioactive contaminant includes, but is not limited to, radio-226.

Still another object of the present invention is to provide a process for reducing the level of radionuclides in phosphogypsum solids in a phosphogypsum material which essentially treats the radioactive contaminant of the phosphogypsum material from the phosphoric acid yields of a wet acidic processing. a phosphate that contains mineral. As a result, large piles of phosphogypsum material can be avoided and / or eliminated in an environmentally friendly process. In view of the above objects, it is a feature of the present invention to provide a process for reducing the level of radionuclides in phosphogypsum solids in a phosphogypsum material which is relatively cost effective, and eliminates radio-226 or other NORMs for limit them below the current NESHAP regulations to create unregulated phosphogypsum for use in construction material or similar.

Another feature of the present invention is to provide a process for reducing the level of radionuclides in phosphogypsum solids in a phosphogypsum material, which is friendly to the environment. A further feature of the present invention is to provide a process for reducing the level of radionuclides in phosphogypsum solids in a phosphogypsum material, which is efficient in time and energy, while reducing the radium-226 to levels below the governmentally regulated standard. An additional feature of the present invention is to provide a process for reducing the level of radionuclides in phosphogypsum solids in a phosphogypsum material, which is cost effective while reducing the radium-226 to levels below government regulation of 10.0 pCi. / g. These and other objects of the present invention have been met by the discovery of a process for reducing a level of radionuclides in a phosphogypsum material having radioactive contaminants, which comprises the steps of: (a) mixing the phosphogypsum material with a decontamination solution to form a mixture; (b) separating the mixture in a liquid stream having a large portion of the radioactive contaminant, and a solid stream having a residual component of the acid decontamination solution; and (c) removing the residual component of the acid decontamination solution from the solid stream. BRIEF DESCRIPTION OF THE DRAWINGS For a further understanding of the nature and object of the present invention, reference should be made to the following detailed description, taken in conjunction with the accompanying drawings, in which like elements have been given numbers. similar or analogous references and wherein: Figure 1 illustrates a generalized flow chart of the process of the present invention; Figure 2 illustrates a detailed flow chart of the embodiment of Figure 1; Figure 3 illustrates a continuation of the closed-loop neutralization process of Figure 2; and Figure 4 illustrates a detailed flow chart of a preferred embodiment of the process of the present invention that includes a multi-stage acid wash, and a new multi-stage paste and acid removal steps. Detailed Description of the Invention The present invention relates to a process for the removal or reduction of radionuclides in a phosphogypsum material. The process of the present invention contemplates the following steps. The first step includes mixing the phosphogypsum material in a decontaminating solution to form a mixture to effect the adsorption of a large portion of the radioactive contaminant by means of the decontamination solution. Subsequently, the process includes separating the mixture into a liquid stream having a large portion of the radioactive contaminant and a solid stream having a residual component of the decontamination solution. In addition, the process includes the neutralization of the solid current, preferably, by washing with fresh water and subsequently neutralizing the water, or alternatively, using a solution of neutralizing agent adapted to neutralize the residual component of the decontamination solution contained in the solid stream. Additionally, what is provided is a process to reduce the level of radionuclides in phosphogypsum solids where the solids are contaminated with a radioactive component. The process contemplates the following steps. The first step involves violently stirring the phosphogypsum crystals with a decontaminating solution to maximize contact of the surface area between the phosphogypsum crystals and the decontamination solution to effect the adsorption of a large portion of the radioactive contaminant in the decontamination solution during a retention time and to create a mixture. Subsequently, the process includes the step of separating from the mixture a liquid stream having a large portion of the radioactive contaminant and a solid stream having a residual component of the decontamination solution. In an exemplary embodiment, during the wet acid processing of a phosphate containing mineral to produce phosphoric acid, a phosphogypsum paste is created. The paste includes phosphogypsum solids in a liquid. In an exemplary embodiment, the pulp is a production stream of the acidic wet process that produces phosphoric acid, but could be any paste of phosphogypsum solid that is contaminated by NORM. Therefore, phosphogypsum solids do not come from the ground or rocks. Instead, the phosphogypsum solids of the present invention are small crystals such as those conventionally produced during the wet processing of the mineral-containing phosphate in the production of phosphoric acid. Phosphogypsum solids form a material in the mind or mogene with respect to particle size, although some difference in size can be tolerated in the process. These solids are crystals having radio-226, uranium-238 and the like adhered thereto. In addition, solids often form clusters thereby trapping radium-226, uranium-238, and the like, within the crystalline lattice work of the cluster. Referring now to the drawings, and in particular to Figure 1, the phosphogypsum decontamination process 1 00 of the present invention begins with step S5 wherein the solids (phosphogypsum material) of the pulp, which have solids of Phosphogypsum contaminated, are passed to step S 10, which is a process of washing and separation A (one step of prefiltration). The washing and separation process A preferably cleans the phosphogypsum material by washing the residues of the mother liquor away from the phosphogypsum solids. The water used in the work phase can be fresh water or process water, depending on the water balance requirements of the particular plant or location. If there is not a water balance problem present, fresh water can be used, with water for recovery of the water used together with residual phosphoric acid within the same process or a different process in the plant, or within a product, such as a diammonium phosphate (DAP). However, if water balance is required, the water used may be process water, preferably in the pre-filtration step, with the filtrate returned to the process in order to improve the recovery of? 2? 5. The washing and separation process A is passed to a decontamination process B in step S20 in the washed contaminated phosphogypsum solids. In an exemplary embodiment, the washing phase of the washing and separation process A attempts to remove a portion of these contaminants that coat the phosphogypsum solids such as, without limitation, fluorine or phosphoric acid, which are very soluble in water. In other words, the coating of contaminants soluble in water or other suspended pollutants, it is easily eliminated with the application of water or other suitable liquid in a washing way, which allows said contaminants to be removed from the liquid stream. In the washing phase, the phosphogypsum feed generally has high phosphate levels, due to the limitations of filter operation. It is not usual for the gypsum hemihydrate to contain 7% P2O5, while the gypsum dihydrate content is much lower, at around 2% P205. Although most processes use dihydrate as a starting material, in hemihydrate-based processes, it is desirable to install transformation tanks to convert gypsum hemihydrate to dihydrate, which has the effect of releasing P2O5 from the crystal of the hemihydrate and inside the pasta. Therefore, the current process can use this initial washing / separating step (prefiltration) as a dihydrate filter to capture the excess P205 in the case where the plant is based on the use of hemihydrate. The prefiltration or washing / separation step may not be necessary if the phosphogypsum used in the process has been stored in piles for a period of time sufficient to allow the cleaning of impurities (eg, F and phosphoric acid) from the solids, or there is adequate filtration available in the process. Alternatively, it may be desirable to skip the prefiltration process in order to retain 2O5 in the phosphogypsum. The resulting product after the elimination of radionuclides, * could be beneficial as a nutrient at the time of its neutralization, together with the neutralization of the acid used in the last stages (preferably nitric acid). Alternatively, in the absence of the pre-filtration process, P205 may be allowed to enter the acid decontamination solution, particularly, in the step of using nitric acid, for the use of N-P fertilizer yields.

The decontamination process B of step S20 removes the radioactive contaminant from the solids using a decontamination solution in an environment, which maximizes the contact of the surface area of the decontamination solution with the contaminants. The environment that maximizes contact of the surface area is carried out by violent agitation. The violent agitation preferably is at a level which is not destructive to the phosphogypsum solids, but which breaks up the accumulations of crystals, so that trapped radium-226 can be exposed to the decontamination solution. More preferably, the violent agitation is limited to a level close to the cut, where blocking of obstruction of the phosphogypsum solids does not take place. It should also be noted that phosphogypsum solids tend to settle. This can be converted using a liquid / solids ratio that maximizes the settlement or formation of crystal accumulations. Preferably, this ratio is 20/80 to 80/20 liquids / solids. More preferably, violent agitation in a ratio of 70/30 liquids / solids attempts to minimize the settlement of solids or groupings of solids. Therefore, a more homogeneous distribution of the solids is created in the decontamination solution, which maximizes contact of the surface area. The decontamination process B is preferably carried out for a retention time within a range of 30 to 120 minutes, more preferably 30 to 90 minutes so that the solids are exposed to the decontamination solution in order to solubilize sufficiently, the radioactive contaminant to a point where it can be carried away in the decontamination solution. The decontamination process B removes a large portion of the radioactive contaminant from the phosphogypsum solids and then from the process 100 at outlet 01. additionally, the decontamination process B recovers the decontamination solution or a portion of it for reuse in the decontamination process B. As can be seen, the recovery of the decontamination solution minimizes the overall costs of the process. 00, so that the replenishment of the decontamination solution is gradual so that the concentration of the decontamination solution is maintained. This also reduces the level of nitrate remaining in the plaster which minimizes the water washes needed to neutralize the cake. In a preferred embodiment, a decontamination solution should be at a pH in a range of 0 to 4, more preferably 0 to 2, and even more preferably of 1/2 to 1. However, a pH of 2 can also create a desirable result. In addition, the decontamination solution can be in a concentrated acid solution, preferably having a concentration range of 10% to 65% of the decontaminant. The decontamination solution can be any acid sufficient to effect the removal of radionuclides, including but not limited to, nitric acid, carbonic acid, hydrochloric acid, hydrobromic acid, and hydrofluoric acid. A solution of nitric acid is preferred. After the retention time has elapsed, step S20 is followed by step S30 where the decontaminated solids from process B are passed to another washing process C. During the washing process C, a portion of the decontaminant is recovered residual of the decontamination solution, which has been retained by decontaminated solids. The decontamination recovered is preferably used again after reconcentration, adding to the decontamination solution in the decontamination process B, or in the preferred case of nitric acid which can be used to produce a nutrient rich in NK or NPK which is a derivative product, now neutralizing the weak acid solution with potassium hydroxide thereby forming potassium nitrate. Controlling the level of nitrate present in the cake and varying the volume of the washing water, the potassium nitrate index produced could be controllable on demand. Step S30 is followed by step S40 wherein the remaining portion of the residual decontaminant of the decontamination solution is neutralized with a neutralizing agent in process D. In the preferred embodiment, the neutralizing agent is selected so that it can be create as production 03 a sellable derivative or an earth nutrient. In addition, process D recycles the fresh water used in the washing or mixing phase.

Additionally, the stream of solids in production 02 contains neutralized and unregulated gypsum. As will be readily appreciated, the process 100 of the present invention processes the phosphogypsum material so that: (1) a sealable gypsum can be created with capacity for use in building materials or other products (since the gypsum contains radioactive contaminants) below government regulation); (2) the radioactive contaminant is eliminated by the process; (3) the liquid constituent of the process is recovered and recycled in the process, as desired; (4) A portion of the decontaminant is recovered and reused. Thus, the process 100 essentially treats the phosphogypsum material created during wet acid processing of a phosphatic containing minerals in a manner that decreases the radioactive contaminant below government regulation. As a result, the process can prevent the formation of large piles of phosphogypsum, and can even eliminate the existing or abandoned piles currently in an environmentally friendly manner. In an alternative embodiment, multiple steps of steps S30 precede step S40 so that the amount of neutralization agent required is minimized. In addition, step S40 includes a washing step with a caustic compound or a neutralization agent with the separation of liquids and solids. Subsequently, a fresh water wash is followed in a sub-closed circuit, as best seen in Figure 3.

In the most preferred embodiment, each process from B to D preferably receives a stream of solids which is subsequently added to a liquid constituent in a ratio of 70/30 liquids / solids. A ratio range of 30/70 to 70/30 of liquids / solids is adequate for each washing phase. Figure 4 provides a flow diagram for a preferred embodiment of the current process. In this diagram, the phosphogypsum starting material (containing radionuclide contaminant) 201 is added to the surface of Filter 1, followed by washing with washing water 202 (preferably from the process water). The filtrate of dihydrate 203 is then removed and sent for further processing, such as in a hemihydrate filter (not shown). The washed phosphogypsum material (which still contains radionuclides) 204 is added to Reactor A together with the decontamination solution (preferably nitric acid). The decontamination solution can be virgin nitric acid, recycled nitric acid from Filter 2, nitric acid added again from Reactors B and C or any combination of the above. Although the figure shows three rectors in which the nitric acid is mixed with the phosphogypsum, this is only a preferred embodiment. This step of the process can be carried out in a single reactor or in a plurality of reactors. Once the dough reaches the final reactor (in this figure, Reactor C), the dough is ready for separation. In any of the road reactors the nitric acid preparation 205 may be added, as necessary, to maintain the solid / liquid ratio. The paste is then placed in Filter 2 through line 206. The filtrate is "pregnant" nitric acid (containing radionuclide contaminant) 207. This is sent back to one or more of the Reactors from A to C Additionally, a portion of the pregnant nitric acid 207 is removed from the recycle line for the removal of fine particles and for the removal of radionuclides (line 208). The removal of the fine particles (small particles of phosphogypsum) can be carried out in any conventional way, such as porous membranes or filter materials. The removal of radionuclides is preferably done using one or more ion exchange beds. Preferably, a plurality of ion exchange beds are used so that at the time of saturation of one of the radionuclide exchange beds, the saturated bed can be removed or replaced, without interrupting the process. As noted above, ion exchange beds can be regenerated to recover radionuclides using conventional chemistry. Alternatively, the exchange beds can be discarded (according to the appropriate regulatory care). The nitric acid solution leaving the exchange beds can be recycled to the process, as desired. Returning to filter 2, the resulting phosphogypsum product (now without any significant amount of radionuclides present) is added to the Gypsum Tank, (along with any traces as noted above, if desired) along with the wash water . The washing water can be fresh water, or the last washing steps (line 21 3) or a combination of these. The washing step of the Gypsum Paste can be a simple wash, or as shown in the case of Figure 4, a plurality of washing steps. The intention of these washes is to remove residual nitric acid or nitrates (or other acid decontamination solution) from the phosphogypsum. Each step preferably comprises the preparation of a paste of the phosphogypsum with water, followed by the separation of the solids from the washing water. The separation step (as well as any or the above separation steps) can be formed in a variety of ways, including but not limited to, centrifugation, filtering, and thickening clarification / sediment thickening. Preferably, as shown in Figure 4, the separations are carried out using a filtration apparatus, more preferably a continuous filter (although a batch process can also be performed using conventional batch filters). The entire process as shown in Figure 4 is preferably a continuous process, with continuous filters, such as band type filtration devices. However, if desired, the process can be carried out in a batch form using any type of batch filtration apparatus, and even using the same continuous type filters. Once the wash / separation steps have been completed, the resulting phosphogypsum product is sufficiently free of nitric acid for use in construction grade gypsum products, preferably with less than 100 ppm nitric acid, and covers the governmental regulations for radionuclide level, as explained above. In a further embodiment, the wash water may be moderately basic (such as, for example, a solution of potassium carbonate or potassium hydroxide), providing a more effective removal of the nitric acid and subsequent neutralization of the residual nitric acid, forming Preference potassium nitrate that can be recovered and used as a plant nutrient, if desired. Alternatively, as shown in Figure 4, the mildly acidic wash water from the Gypsum Paste tanks can be subsequently neutralized, using similar basic solutions. In an alternative embodiment, an additional Protection bed can be used between the filtering lines 211, and the neutralization step, in order to eliminate any residual radionuclei present in the filtrate. EXAMPLE: Referring now to Figure 2, generally the plaster decontamination process 100 begins with step S5, the incoming paste has approximately 70% liquids and 30% phosphogypsum solids. The paste is separated into a solid stream 2 (referred to as the phosphogypsum material), and a liquid stream (not shown), using well known liquid / solids separation techniques. In the exemplary embodiment, the liquid stream (not shown) can be reused in the plant which originally produced the paste. The process 100 of the present invention essentially processes the solid stream 2 from the paste of step S5 having contaminated phosphogypsum solids governed by government. Phosphogypsum solids are contaminated with radio-226 NORM. As a result of the previous process, in the table 1 an example of the productions is established (Observe: tpd means ton per day) TABLE I Step S5 is followed by step 1 10 where the solid stream 2 (phosphogypsum material) is processed through a first washing step. In the example mode, the contaminated solids are converted back into pulp or are washed at least once with fresh water from line 4. During the washing phase of step 1 10, the fresh water mixture and the Contaminated solids have approximately a ratio of 70/30 liquids / solids. Preferably, the washing phase includes the violent agitation of the mixture of contaminated solids and fresh water to effect a washing action. Although a ratio of 70/30 liquids / solids is preferred, a range of 30/70 to 70/30 ratio of liquids / solids for the washing action and the removal of the water soluble contaminants is suitable. The violent agitation or violent mixing creates an environment where the settlement or grouping of the phosphogypsum solids is minimized, and the contact of the surface area of the gypsum solids with the fresh water is maximized. Step 1 1 0 is followed by step 1 15 where the mixture on line 5 is separated into a liquid stream 6 and a solid stream 7. Liquid stream 6 is communicated out of process 100. steps 1 10 and 1 15 constitute a washing and separation process A. The solids stream 7 contains essentially contaminated phosphogypsum solids. As a result of the separation and washing process A, the example yields are set forth in Table II.

TABLE II The stream of solids 7 from step 1 1 5 enters the decontamination process B to remove a large portion of the radioactive contaminants from the phosphogypsum solids, such as radium-226 or NORM. Step 1 1 5 is followed by step 120 where the stream of solids 7 is mixed with the decontamination solution (which in the current example is a solution of concentrated nitric acid (H NO 3)) in line 8 at temperature environment for a retention period of 1 to 60 minutes. In the preferred embodiment, the retention time is substantially 30 minutes, although lower times may be used. Different acids were used to produce the radium-226 soluble. The nitric acid solution was the best decontaminant to solubilize radio-226 for the crystal of the phosphogypsum solid. In addition, the decontamination solution should more preferably have a pH of from ½ to 1, with 1 being most preferred. Step 120 is followed by step 125, where the mixture on line 9 is separated from the nitric acid solution (H N03) in a liquid stream 10, and a stream of solids 11. The washing in step 120 may be performed one or more times. In the example mode, the stream of solids 1 is further processed by process C. As a result of process B, an example of the productions is set forth in Table I I. TABLE III In a preferred embodiment, the phosphogypsum solids of the stream of solids 7 are mixed and reacted with a concentrated solution of nitric acid (HN03) concentrated at 65% in a ratio of 70/30 liquids / solids. The mixture is violently stirred during washing in step 120 at room temperature, which effects decontamination in which a decontaminating portion of radio-226 or NORM is adsorbed, or impregnated in the nitric acid solution (H N03). Although a concentration of 65% nitric acid is preferred for the concentrate, other concentrations may be substituted. However, lower concentrations may require longer retention times to remove radium-226 at levels that are within or below government regulation of < 1 0 pCi / g. In step 120 no heat is added. Therefore, the washing is carried out at room temperature. In a refinery, the ambient temperature may be the result of climate control methods, such as air conditioning. Otherwise, the ambient temperature may be the result of the local climate temperature. The liquid stream 10 containing the nitric acid solution impregnated with radio-226 is contacted with an ion exchange resin in step 130. Ion exchange, such as a Dowex RSC manufactured by DOW Chemical or Eichrome , removes radium-226 from the liquid stream 1 0 thus regenerating the nitric acid solution. Therefore, the nitric acid solution is essentially free of radium and can be returned to step 120 in line 8. As can be seen, the regenerated nitric acid solution is recovered for repeated use during the washing phase in the Step 120 Process B does not require the continuous cycling of the impregnated nitric acid solution to the ion exchange resin, until the concentration of nitric acid decreases, or the level of the radioactive impregnation pollutant is high enough to compromise the effectiveness of the nitric acid solution. In other words, after the retention time has elapsed, the separate impregnated nitric acid solution does not have to come into contact with the ion exchange resin. During the phase of removal of the radius in process B, the ion exchange resin is filled with radio-226. Once the ion exchange resin is essentially full I up to its capacity, the radium-saturated ion exchange resin can be replaced by another and the ion-exchange resin that has been filled can be discarded, sold or regenerated. right way. Therefore, the radioactive contaminant radio-226 is eliminated from the process at outlet 01. About four to six grams of pure radium-226 are regenerated per million tons of phosphogypsum solids treated using process 1 00 of the present invention. The regenerated ion exchange resin is again ready to be used in process B. However, some resins can not be regenerated, and can be either sold as a radio-charged resin, or discarded as a contaminated resin. The decontaminated solids in line 1 1, are sent to step 135, and are reshaped in pulp or washed with fresh water, in a ratio of 70/30 liquids / solids using mixing or washing in a retention time about 5 minutes. The washing retention time can be increased, or if necessary, the washing phase can be repeated. The mixture from step 1 is passed from line 12 to step 140 where the liquid / solids separation is carried out. In step 145, the liquid stream 1 3 is processed in a water recovery step to capture a portion of the residual nitric acid (H N03), and separate and recover the liquid (water) from the liquid stream 1 3. Nitric acid (H N03) is injected into line 14a into liquid stream 1 0. Therefore, nitric acid (H N03) is recycled or reused. The water stream 14b from step 145 is recycled and reused in process C in step 1 35. As a result of process C, an example of yields is set forth in table IV. TABLE IV MATERIAL WEIGHT SOLIDS: F 740 ppm Nitrate 4520 ppm Si 176 ppm Ra226 3 pCi / g U238 9 pCi / g LIQUIDS: F 395 ppm Nitrate 21900 ppm P04 2 ppm S04 22300 ppm Ra226 1529 pCi / L U238 0.06 pCi / L The stream of solids 5 from process C is passed to the water washing step 1 50 of process D, and is washed a second time using the same ratio of liquids / solids. However, in one embodiment, prior to liquid / solid separation in step 1 55, a neutralizing agent, such as a caustic compound (e.g., sodium carbonate (NACO3)) is added during the washing phase in step 1 50 to adjust the pH of the solids stream 15 to a pH between 6.5 and 8.0. the neutralizing agent reacts with the residual decontaminant (nitric acid HN O3) in the wash water, which is passed on line 16 to step 155. The mixture of the stream of solids 15, and the neutralizing agent is then separated. in a stream of liquids 17, and a stream 1 of solids in the outlet line 02. The stream of solids has a content of radium-226 which is lower than the current regulatory limits (< 5.0 pCi / g) for the construction material. In addition, the radio-226 content is lower than the current regulatory limit of (1.0 pCi / g) for agricultural applications. In a preferred alternative embodiment, the solids of the process; C become paste with water, and then the solids are separated, preferably by filtration, to produce a cake of solids containing residual H N03 in the solids. Therefore, 1 the number of pulp preparation / separation repetitions depends on the H NO3 level that can be tolerated in the final gypsum product. In addition, any residual acid can also be neutralized at any of the pulp / separation steps, using a basic solution. Any basic solution, such as alkali hydroxides, can be used, but the most preferred is potassium hydroxide since it would result in the production of potassium nitrate, a useful derivative, and which is a plant nutrient. The liquid stream 17 is passed to step 160, where the liquid portion of the stream is recovered. The portion of the liquids C is recycled again on line 1 8 to the washing phase of step 150 in process D. Referring now to Figure 3, the neutralization process D also includes a fresh water wash in the step 170 where the stream of solids is again washed in the outlet line 02. The mixture of the washing step 1 70 is passed to step 175 where the liquid / solids separation takes place. The liquid stream in line 20 is recovered in step 180 where further, with an optional ground nutrient, such as potassium nitrate is generated in line 03 ', the stream of solids 02' is gypsum additionally neutralized with a pH of 7 ppm. Water 'recovered from step 180 is sent back on line 22 to step 170. During the neutralization process D, the residual decontaminant is neutralized with a basic compound, such as sodium carbonate, potassium hydroxide or the like. Therefore, the recovery phase produces potassium nitrate (when a potassium salt is used) at the outlet line 03, which can be used as a nutrient for the soil. In another embodiment, instead of adding the basic compound as part of the water wash of step 150, the stream of neutralized solids 02 is further washed with the caustic in a process to recover the water and produce decontaminated and neutralized gypsum having approximately 7 ppm of nitrate. As a result of the neutralization process D, an example of the performances is established in table V. TABLE V As can be seen, the nitrate absorbed in the solids stream 15 has been reduced from 4,520 ppm to 7 ppm. Therefore, a significant portion of nitrate has been recovered. In an alternative embodiment, as indicated above, the additional washing in step 150 can be replaced by the addition of the basic compound or neutralizing agent. As a result of the above process 100, the products created are (1) a solid gypsum material not regulated in the outlet line 02 and 02 '; (2) a neutralizing agent or derivative thereof in the outlet line 03 and 03 '; and (3) radio-226 on the starting line 01. The process 100 of the present invention can be carried out on an output side of phosphoric acid directly receiving a phosphogypsum paste having phosphogypsum material. On the other hand, the process 100 can create a paste using the dry contaminated phosphogypsum material stacked in the aforementioned stacks. In summary, the process 100 is carried out without the need to heat the water or the decontamination solution, or by applying a heating component to process A, B, C or D. It should be noted that essentially rapid results are created without the need of energy expenditure for warming. The ambient temperature for process 1 00 is in a range of 21.1 ° C to 37.78 ° C (70 ° F to 100 ° F). EXAMPLES OF WORK Day 1 A: Raw Plaster Paste Filter: Weight of solids: 1 7,758 kg (39.1 5 pounds) (32.8% by weight); sample labeled S-1. The Radio 226 is 14 pCi / g and the Uranium is 1 pC / g. Liquid weight: 36.401 kg (80.25 pounds), sp. gr. = 1 .0583 gm / cc or 34,447 liters (9.1 gallons) (67.2% by weight) with a pH = 1.27; Sample marked L-1. Radio 226 is 461 pCi / L and Uranium is 60 pCi / L. B: New Solids Pulp S-1: The 4540 grams (10 pounds) of the filtered solids from the previous one were washed with 10,600 cc (2.8 gallons) of water from the stirred tap at a rate of 1,000 rpm for one minute using a cutting type mixing blade, and Then it was filtered. 3,561 kg (7.85 pounds) of solids were recovered, sample marked S-2, Radio is 14 pCi / g and Uranium is 12 pCi / g. recovered 25.55 pounds (1 1, 750 ce) of water, sample marked L-2, pH = 1.98, Radio 226 is 207 pCi / L and Uranium is 554 pCi / L. i C: Solid Acid Wash: 1800 grams of solid S-2 (3.96 pounds), plus 4,200 ce of concentrated nitric acid were mixed at a temperature of 33.33 ° C (92 ° F), and a speed of 500 rpm using a blade of mixing that is not cutting. Half of the mixture was removed after a time of 30 minutes and filtered. The other half was mixed for a total time of one hour followed by filtration. Each of the solid portions was converted back into pulp for a mixing time for one minute at a rate of 500 rpm / using 1,600 ce of fresh water from the tap. 30 minute sample: 1 129 grams of solids labeled S-3 were filtered. Radio 226 is pCi / g and Uranium is 9 pCi / g. 2350 ce, of pregnant Nitric Acid solution marked L-3 (dark brown solution). 1 700 ce, of washing water of the new pulp labeled L-4 (yellow color) Radio 226 is 1529 pCi / L and Uranium is .06 pCi / g. One hour sample: 635 grams of marked S-4 solids were filtered. Radio 226 is < 1.58 pCi / g and Uranium is 12 pCi / g. 1500 ce. Of Pregnant Nitric Acid solution labeled L-5 (dark coffee colour). Radio 226 is 4353 pCi / L and Uranium is 86 pCi / L. 1680 CE of washing water of the new pulp label L-6 (pale yellow color). The radius 226 is 1447 pCi / L and the uranium is 36 pCi / L. Day 2 A 21 K Dowex resin was sulfonated to a pH of 2.7 using a 1N Sulfuric Acid solution. The Dowex RSC and Eichrom IX resins were rinsed in water using deionized water. Day 3 A: Nitric acid ion exchange: 900 cc was mixed. of the sample L-4 (water of the new pulp S-3), for 6 minutes with 450 ce. of Eichrom IX resin and then filtered. The filtrate (pure), of the sample of Nitric Acid labeled L-7. The same resin Eichrom IX, 450 ce. it was then mixed with 1,120 ce. of the sample L-6 (water of the new pulp S-4) and mixed for 7.5 minutes. The filtrate was labeled L-8. The radius 226 is 916 pCi / L and the uranium is 9 pCi / L. 350 ce were mixed. of Eichrom IX new with 1350 ce. of sample L-3 (33 minutes, pregnant Nitric Acid) and mixed for 9 minutes. The filtrate was labeled L-9. 300 ce were mixed. of Eichron IX new with 690 ce. of the sample L-5 (one hour of pregnant N-tric acid) for 4.6 minutes. The filtrate was labeled L-1 0. The radius 226 is 2058 pCi / L and the uranium is 9 pCi / L. Note: All resin mixing times are based on an equivalent of 9,464 liters / 929.03cm2 (2.5 galoes / square foot) of resin per minute. It was observed that the modality of the process described here in detail, for example purposes, of course, is subject to many different variations in its structure, design, application and methodology. Because many different and different modalities can be made within the scope of the inventive concept taught here, and because many modifications can be made to the modalities here, described in accordance with the legal descriptive requirements, it should be understood that the details here provided should be interpreted in the illustrative and non-limiting sense.

Claims (1)

1. CLAIMS 1. A process for reducing a level of radionuclides in a phosphogypsum material having a radioactive contaminant, which comprises the steps of: (a) mixing the phosphogypsum material with an acid decontamination solution to form a mixture; (b) separating the mixture in a stream of liquids having a large portion of radioactive contaminant and a solid stream having a residual component of the acid decontamination solution; and (c) removing the residual component of the acid decontamination solution from the solids stream. 2. The process as described in claim 1, wherein the mixture comprises a ratio of 70/30 liquids / solids. 3. The process as described in claim 1, wherein the mixture comprises a ratio of liquids / solids in a range of 80/20 to 20/80. 4. The process as described in claim 1, wherein the mixing step (a) comprises: (ai) violently stirring the mixture for a period of time. 5. The process as described in claim 4, wherein: the time duration is from 30 to 90 minutes. 6. The process as described in claim 4, wherein the duration is 60 minutes. The process as described in claim 1, wherein the mixing step (a) comprises: (ai) violently stirring the mixture at room temperature in a range of 21.1 1 ° C (70 ° F) at 100 ° F (37.78 ° C) for a duration of time. The process as described in claim 1, wherein the removal step comprises forming a paste from the stream of solids with a washing solution, followed by separation of the solids from the liquids. 9. The process as described in claim 8, wherein the wash solution is water. 1. The process as described in claim 8, wherein the washing solution comprises water and a neutralizing agent. eleven . The process as described in claim 10, wherein the neutralizing agent comprises a basic compound. The process as described in claim 1, wherein the basic compound is a member selected from the group consisting of alkali hydroxides, alkali earth metal hydroxides, carbonated alkali metal carbonates and alkali earth metal carbonates. The process as described in claim 1, wherein step (c) comprises the steps of (c) mixing the stream of solids with water to create an aqueous slurry of solids; (cii) separating the slurry of solids in a stream of liquids and a stream of washed solids; (ciii) neutralizing at least a portion of the liquid stream by a neutralizing agent to create a stream of neutralized liquids; and (civ) recover the washed solids stream. The process as described in claim 13, wherein the aqueous solids paste comprises a ratio of 70/30 liquids / solids. 15. The process as described in claim 13, wherein the aqueous solids paste comprises a ratio of liquids / solids in a range of 80/20 to 20/80. The process as described in claim 13, wherein the washed solids stream comprises neutralized gypsum having a radium-226 content of less than 1.0 pCi / g. 17. The process as described in claim 16, wherein the washed solids stream comprises neutralized gypsum having a radium-226 content of less than 5.0 pCi / g. The process as described in claim 1, wherein the solids stream comprises gypsum having a radium-226 content of less than 1 0.0 pCi / g. 9. The process as described in claim 18, wherein the solids stream comprises a gypsum having a radium-226 content of less than 5.0 pCi / g. 20. The process as described in claim 1, which further comprises: (d) contacting the liquid stream having a large portion of radioactive contaminant from step (b) with an ion exchange resin to remove the radioactive contaminant from the liquid stream, and producing a regenerated acid decontamination solution. twenty-one . The process as described in claim 20, which further comprises (e) returning the acid decontamination solution regenerated to step (a). 22. The process as described in claim 1, wherein the acid decontamination solution is a nitric acid solution. 23. The process as described in claim 22, wherein the nitric acid solution is a concentrated nitric acid solution. The process as described in claim 23, wherein the concentrated nitric acid solution has a pH in the range of 0.5 to 2.0. 25. The process as described in claim 24, wherein the concentrated nitric acid solution has a pH in the range of 0.5 to 1.0. 26. The process as described in claim 22, wherein the nitric acid solution is a solution of aqueous nitric acid. 27. The process as described in claim 26, wherein the aqueous solution of nitric acid has a concentration of 50 to 65% nitric acid. 28. The process as described in claim 1, wherein the mixing step (a) is carried out in a plurality of reactors in sequence. 29. The process as described in claim 1, wherein the elimination step (c) is carried out in a plurality of pulp tanks in sequence, so that starting with the second pulp tank, each tank of pasta is separated from the previous pasta tank by means of the separation of the solids from the liquids. 30. The process as described in claim 29, wherein at least a portion of the liquid resulting from the solids separation means of the liquids is recycled to a previous pulp tank and used as a wash water for the means for separating solids from liquids or both. 31 The process as described in claim 1, wherein the liquid stream having a large portion of radioactive contaminant is subjected to the removal of fine particles to generate a stream of fine particles, in a liquid stream free of fine particles which has a large portion of radioactive contaminant. 32. The process as described in claim 31, wherein the stream of fine particles is combined by the stream of solids in step (c). The process as described in claim 31, wherein the liquid stream free of fine particles has a large portion of radioactive contaminant that is contacted with an ion exchange resin to remove the radioactive contaminant from the stream of fluids free of fine particles to produce a regenerated acid decontamination solution.